Structural and genomic correlates of hyperthermostability

While most organisms grow at temperatures ranging between 20 and 50 degrees C, many archaea and a few bacteria have been found capable of withstanding temperatures close to 100 degreesC, or beyond, such as Pyrococcus or Aquife r Here we report the results of two independent large scale unbiased approa ches to identify global protein properties correlating with an extreme ther mophile lifestyle. First, we performed a comparative proteome analyses usin g 30 complete genome sequences from the three kingdoms. A large difference between the proportions of charged versus polar (noncharged) amino acids wa s found to be a signature of all hyperthermophilic organisms. Second, we an alyzed the water accessible surfaces of 189 protein structures belonging to mesophiles or hyperthermophiles. We found that the surfaces of hyperthermo philic proteins exhibited the shift already observed at the genomic level, i.e, a proportion of solvent accessible charged residues strongly increased at the expense of polar residues. The biophysical requirements for the pre sence of charged residues at the protein surface, allowing protein stabiliz ation through ion bonds, is therefore clearly imprinted and detectable in a ll genome sequences available to date.